Apparatus of clamping semiconductor devices using sliding finger supports

ABSTRACT

An apparatus for supporting lead fingers during a wire bonding process and method of preventing the bonding apparatus and clamping assembly from applying force against the die. The present invention includes the use of a movable arm with a portion that is positionable under a portion of the lead fingers of a lead frame during the wire bonding process to provide increased stability of the lead fingers and prevent the bonding apparatus and clamping assembly from applying force against the die. The present invention also provides for the transfer of heat from the heat block directly to the lead fingers during the wire bonding process. The present invention includes the use of a clamp for stabilizing lead fingers during the wire bonding process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/840,289,filed Apr. 23, 2001, now U.S. Pat. No. 6,637,636, issued Oct. 28, 2003;which is a continuation of application Ser. No. 09/358,248, filed Jul.21, 1999, now U.S. Pat. No. 6,227,431, issued May 8, 2001; which is adivisional of application Ser. No. 09/244,702, filed Feb. 4, 1999, nowU.S. Pat. No. 6,299,057, issued Oct. 9, 2001; which is a continuation ofapplication Ser. No. 08/709,639, filed Sep. 9, 1996, now U.S. Pat. No.5,890,644, issued Apr. 6, 1999; which is a continuation-in-part ofapplication Ser. No. 08/631,143, filed Jun. 17, 1996, now U.S. Pat. No.5,673,845, issued Oct. 7, 1997; application Ser. No. 08/597,616, filedFeb. 6, 1996, now U.S. Pat. No. 5,647,528, issued Jul. 15, 1997; andapplication Ser. No. 08/592,058, filed Jan. 26, 1996, now U.S. Pat. No.5,954,842, issued Sep. 21, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to forming wire bonds between thecontact pads on semiconductor devices and individual lead frame fingersof a lead frame.

More specifically, the present invention is related to the apparatus andmethod of supporting the lead fingers of a lead frame during a wirebonding process using a support arm with a lead support portion that ispositionable between the lead fingers and the die prior to the bondingprocess to help substantially stabilize the lead fingers during thebonding process.

2. State of the Art

Well known types of semiconductor devices are connected to lead framesand subsequently encapsulated in plastic for use in a wide variety ofapplications. Typically, the lead frame is formed from a singlecontinuous sheet of metal by metal stamping operations. In aconventional lead frame, the lead frame includes an outer supportingframe, a central semiconductor chip supporting pad and a plurality oflead fingers, each lead finger having, in turn, a bonding portionthereof near the central chip supporting pad. Ultimately, the outersupporting frame of the lead frame is removed after the wire bondsbetween the contact pads of the semiconductor chip device and the leadfingers are made and the semiconductor device and a portion of the leadframe have been encapsulated.

In the assembly of semiconductor devices utilizing such conventionallead frames, a semiconductor die is secured to the central supportingpad (such as by a solder or epoxy die-attach, although a double-sidedadhesive tape-type attach has also been suggested in the art) and thenthe entire lead frame, with the semiconductor die thereon, is placedinto a wire bonding apparatus including a clamp assembly for holding thelead frame and die assembly, and clamping the lead fingers for bonding.

In contrast to a conventional lead frame, U.S. Pat. No. 4,862,245,issued Aug. 29, 1989 to Pashby et al., illustrates a so-called“leads-over-chip” arrangement (“LOC”) on the semiconductor die. Aplurality of lead fingers of the lead frame extends over the activesurface of a semiconductor die toward a line of bond pads thereonwherein bond wires make the electrical connection between the leadfingers and the bond pads. An alpha barrier, such as a polyamide tape(for example, Kapton™ tape), is adhered between the semiconductor dieand the lead fingers. This configuration, which eliminates the use ofthe previously-referenced central die attach pad, may assist in limitingthe ingress of corrosive environment contaminants after encapsulation ofthe semiconductor device, achieves a larger portion of the lead fingerpath length encapsulated in the packaging material, and reduceselectrical resistance caused by the length of the bond wires (i.e., thelonger the bond wire, the higher the resistance) and potential wiresweep problems in the encapsulation of the semiconductor deviceaggravated by long wire loops.

In a standard wire bonding process, the bond wires are attached, one ata time, from each bond pad on the semiconductor device to acorresponding lead finger. The bond wires are generally attached throughone of three industry-standard wire bonding techniques: ultrasonicbonding—using a combination of pressure and ultrasonic vibration burststo form a metallurgical cold weld; thermocompression bonding—using acombination of pressure and elevated temperature to form a weld; andthermosonic bonding—using a combination of pressure, elevatedtemperature, and ultrasonic vibration bursts.

To form a good bond during the wire bonding processing, it is preferableto perform the bonding at an elevated and somewhat stable temperature.Therefore, as noted above, the lead frame assembly, including theattached semiconductor die, is generally placed on a heater block. Thesemiconductor die is then clamped (via the lead frame) to the heaterblock by a clamping assembly. With a conventional lead frame, the leadfingers are clamped directly against the underlying heater block.Whereas, in a LOC lead frame, the lead fingers are biased between theclamp and the active surface of the semiconductor die heater block.Thus, in a LOC lead frame arrangement, the clamping assembly and bondingapparatus apply pressure against the die, thereby causing possibledamage. In addition, heating of the lead fingers in a LOC lead frame forwire bonding must be done through heating the die, as opposed todirectly heating the lead fingers by the heater block in a conventionallead frame.

Therefore, in a LOC lead frame configuration it would be advantageous todevelop an apparatus to prevent the clamping assembly and bondingapparatus from applying force against the die. In addition, it would beadvantageous to develop an apparatus for transferring heat directly fromthe heat block to the lead fingers.

In a LOC structure, the Kapton™ tape comprising the alpha barrier ordielectric between the semiconductor and the lead fingers becomes softat the elevated temperature. The softening of the tapes allows the leadfingers and/or semiconductor die to move in response to ultrasonicenergy or pressure (force) exerted by the wire bonding head (capillary).As a result, the mechanical integrity of the wire bond to the leadfingers is diminished. Furthermore, a “bouncing” motion is imparted tothe lead fingers by the wire bonding head movement, which motion may beexacerbated by the heat softened tape. This bouncing motion can alsoresult in poor wire bonds which subsequently fail.

Thus, die fabricators are somewhat compelled to select the die attachcompound (or other means) and alpha barrier tape based on the thermalstability of the materials rather than on the basis of the mosteffective material for a given application.

Therefore, it would be advantageous to develop an apparatus that wouldreplace the alpha barrier tape while stabilizing the semiconductor dieand the lead fingers during the wire bonding process.

Typical apparatus and methods for clamping the lead frame during thewire bonding process or for clamping and advancing the lead frame areillustrated in U.S. Pat. Nos. 4,765,531, 5,082,165, 5,238,174,5,264,002, 5,307,978, 5,322,207, and 5,372,972. However, such apparatusand methods do not address the problem of supporting the lead fingersduring the wire bonding process or preventing the application of forceon the die.

Such prior art apparatus and methods have been directed at advancing andorienting the lead frame, but have not attempted to solve the problemsof forming reliable wire bonds between the contact pads of semiconductordevices and lead fingers of lead frames.

There have been other attempts to overcome the problem of the bouncingmotion imparted to the lead fingers by the wire bonding head movement.For example, for bonding LOC structures, rigid clamping plates havingbond site windows therein have been reconfigured so that the bond sitewindow is reduced in size and the downwardly-extending lip or peripherycontacts the lead fingers extending over the die and clamps the leadfingers directly thereto. However, the rigid clamp has been found to betoo rigid and unyielding for use with a LOC configuration, and maypossibly damage the die. Moreover, the use of a rigid clamp adds to theforce exerted against the die and does nothing to prevent theapplication of force by the bonding apparatus.

The present invention is directed to an improved wire bonding apparatusand method for forming such wire bonds.

BRIEF SUMMARY OF THE INVENTION

The present invention is related to the apparatus and method ofsupporting lead fingers during a wire bonding process. The presentinvention includes the use of a movable arm having a lead supportportion for positioning under the lead fingers of a lead frame and/orbetween the die and the lead fingers during the bonding process toprovide increased stability of the individual lead finger for improvedbonding and to prevent the bonding apparatus and clamping assembly fromapplying force to the die. The present invention also provides for heatto be directly transferred from the heat block to the lead fingersduring the wire bonding process.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be better understood when the description ofthe invention is taken in conjunction with the drawings wherein:

FIG. 1 is a side view of the present invention used in the wire bondingof a semiconductor device arrangement having a conventional lead frame;

FIG. 2 is a cross-sectional view taken along A—A of the presentinvention, as depicted in FIG. 1, and further shows one method ofdynamic attachment;

FIG. 3 is a cross-sectional view taken along A—A of the presentinvention, as depicted in FIG. 1, and further shows another method ofdynamic attachment;

FIG. 4 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

FIG. 5 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

FIG. 6 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

FIG. 7 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

FIG. 8 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

FIG. 9 is a side view of the present invention used in the wire bondingof a semiconductor device arrangement having a LOC lead frame withoutthe leads adhered to the semiconductor device;

FIG. 10 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

FIG. 11 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

FIG. 12 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

FIG. 13 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

FIG. 14 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

FIG. 15 is a side view of the present invention used in the wire bondingof a semiconductor device arrangement having a LOC lead frame with theleads adhered to the semiconductor device;

FIG. 16 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

FIG. 17 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

FIG. 18 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

FIG. 19 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

FIG. 20 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

FIG. 21 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

FIG. 22 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

FIG. 23 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

FIG. 24 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

FIG. 25 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

FIG. 26 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

FIG. 27 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a hybrid lead frame with leads on differing levels;

FIG. 28 is a view of the alternative embodiment of the present inventionillustrated in drawing FIG. 27 with the alternative embodiment rotatedninety degrees (90°) to illustrate the lead support for the lead fingersof the hybrid lead frame;

FIG. 29 comprises a flow chart of an exemplary process sequence forplastic package molding of a semiconductor device wire bonded to a leadframe using the lead support of the present invention;

FIG. 30 is a side schematic view of a typical transfer mold illustratinga pre-molding encapsulant position;

FIG. 31 is a side schematic view of a typical transfer mold illustratinga post-molding encapsulant position;

FIG. 32 illustrates a top schematic view of one side of a transfer moldof FIGS. 28 and 29 depicting encapsulant flow and venting of the primarymold runner and the mold cavities wherein the die assemblies arecontained;

FIG. 33 depicts a first encapsulant flow scenario for a mold cavityduring molding a lead frame and semiconductor manufactured using thepresent invention of a lead bonding support;

FIG. 34 depicts a second encapsulant flow scenario for a mold cavityduring molding a lead frame and semiconductor manufactured using thepresent invention of a lead bonding support; and

FIG. 35 depicts a third encapsulant flow scenario for a mold cavityduring molding a lead frame and semiconductor manufactured using thepresent invention of a lead bonding support.

DETAILED DESCRIPTION OF THE INVENTION

Referring to drawing FIG. 1, a semiconductor device (die) 10 is shownbeing supported by the paddle 12 of a conventional lead frame. A heatblock 20 is used to heat the paddle 12 and die 10 during the wirebonding process. As shown, a suitable wire 16 has one end 17 thereofbonded to a bond pad of the die 10. The wire 16 may be of any suitabletype for connection and bonding purposes, such as gold, gold alloy,aluminum, aluminum alloy, etc. The other end 18 of the wire 16 is shownbeing bonded to the end 15 of a lead finger 14 of the lead frame by asuitable bonding apparatus 26. The bonding apparatus 26 may be of anysuitable type well known in the bonding area, such as a taillessthermosonic or ultrasonic capillary type bonding apparatus whichdispenses wire during the bonding process. If desired, in the wirebonding operation, further shown in contact with lead finger 14 is aportion of a conventional clamp 22 used to clamp portions of the leadframe during such bonding operations. The conventional clamp 22 may beof any well known suitable type, such as those described hereinbefore,and is generic in shape. Further shown in drawing FIG. 1 is a movableand/or adjustable arm 24, having a lead support portion 25, attached toor an integral part of the movable and/or adjustable arm 24. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned between the die 10and the lead fingers 14. The movable and/or adjustable arm 24 and leadsupport portion 25 thus allow for any desired size semiconductor device10 to be wire bonded without a change to the heat block 20. In addition,movable and/or adjustable arm 24 having lead support portion 25 conductsheat from the heat block 20 to the lead fingers 14.

During the wire bonding process, it is desirable for the heat block tobe heated to substantially 230 degrees Centigrade. Although the heatblock may be any suitable temperature during the bonding operation, theheat block 20 temperature should not exceed 300 degrees Centigrade toprevent thermal damage to the die 10. It is further preferred that thebond of the end 18 of the wire 16 made to the end 15 of the lead finger14 of a conventional lead frame be made at a temperature ofsubstantially 190 degrees Centigrade for bonding effectiveness. It isalso preferred that the bonding apparatus exert a bonding force ofsubstantially 50 to 100 grams when bonding the end 18 of the wire 16 tothe end 15 of lead finger 14 for effective bond formation of the wire 16to lead finger 14.

The movement of the movable and/or adjustable arm 24 may be effectuatedby various means 28. Such means are well known in the manufacturing areaand may include an air cylinder, a solenoid, a magnet system, a motor,sprockets, a cable and pulley system, a lead screw, a cam arrangement,etc.

The movable and/or adjustable arm 24 is dynamically attached to the heatblock 20 so that as the heat block moves into position during the wirebonding process, the movable and/or adjustable arm 24 having leadsupport portion 25 moves into position under the lead fingers 14. Stillreferring to FIG. 1, movable and/or adjustable arm 24 is shown astraveling against the heat block 20 such that the direction of travel issubstantially parallel with respect to the lower surface 19 of the leadfingers 14 of a conventional lead frame.

Referring to drawing FIG. 2, one method for dynamically attachingmovable and/or adjustable arm 24 to heat block 20 is by atongue-and-groove type connection. A tongue 30, shaped in the form of adove tail, is formed in the heat block 20. A mating groove 32 is formedin movable and/or adjustable arm 24 so that the tongue 30 may slidewithin the groove. Thus, movable and/or adjustable arm 24 is allowed toslide with respect to heat block 20 while maintaining contact with theheat block for efficient heat transfer. Alternatively, a tongue could beformed in the movable and/or adjustable arm and the groove could beformed in the heat block. Other tongue-and-groove connections may beeffectuated by forming different shaped tongue and grooves. For example,a square shaped tongue may be formed in heat block 20 and a matinggroove formed in movable and/or adjustable arm 24. To reduce friction,linear bearings 42 may be used as well as low friction pads 44 orlubricants.

Referring to drawing FIG. 3, another method for dynamically attachingmovable and/or adjustable arm 24 to the heat block 20 is by havingmovable and/or adjustable arm 24 travel in a track 48 that is formed inheat block 20. Thus, movable and/or adjustable arm 24 is allowed toslide, with respect to heat block 20, while maintaining contact with theheat block for efficient heat transfer. Again, movement may befacilitated by the use of linear bearings 42 or low friction pads 44 orlubricants. Other methods for dynamically attaching the movable and/oradjustable arm 24 to the heat block 20 are tracks, a track-and-carriagesystem, a hinge, a cam arrangement, etc.

Referring to drawing FIG. 4, movable and/or adjustable arm 24 may beattached to heat block 20 such that the direction of travel, withrespect to lower surface 19 of lead fingers 14, is angular or arcuate. Aradius 54 may be formed in heat block 20 and movable and/or adjustablearm 24 such that the direction of travel of lead support portion 25 andmovable and/or adjustable arm 24 is arcuate, with respect to lowersurface 19 of the lead fingers 14 of a conventional lead frame, as thelead support portion is positioned prior to wire bonding.

Referring to drawing FIG. 5, the surface of the heat block 20 andmovable and/or adjustable arm 24 may also be angled 56, with respect tolower surface 19 of the lead fingers 14, such that the direction oftravel of lead support portion 25 and movable and/or adjustable arm 24is angular, with respect to lower surface 19 of lead fingers 14, as thelead support portion 25 of movable and/or adjustable arm 24 ispositioned prior to the wire bonding process.

The movement of the movable and/or adjustable arm 24 and the heat block20 may be integrated so that as the heat block moves into position itcauses the movable and/or adjustable arm to move into position. In FIG.5, a notch 50 is shown formed in movable and/or adjustable arm 24 andextends into a slot 52 formed in a stationary member (not shown). Thus,as the heat block 20 moves upward to contact the die 10, the heat blockpushes against the movable and/or adjustable arm 24, which is forced totravel upward and inward by the notch 50 traveling in the slot 52.

Referring to drawing FIG. 6, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers during the wire bonding process. Theconventional clamp 22 acts as a primary clamp and includes a bond sitewindow 60. The bond site window 60 is sized to allow access for abonding apparatus 26 to a plurality of bond pads of semiconductor die 10and to a plurality of lead fingers 14 of a conventional lead frame.

The bond site window 60 includes a secondary clamp 62. The secondaryclamp 62 is mounted to a resilient plate 64 with a first set screw orbolt 66. The proximal end of each resilient plate 64 is attached to theconventional clamp 22 with a second set screw or bolt 68. It is, ofcourse, understood that secondary clamp 62 can be attached to theconventional clamp 22 in any number of known configurations, includingforming the secondary clamp 62 with an integral resilient portion whichis secured to the conventional clamp 22 or forming (for example, as bymachining) the secondary clamp 62 as an integrated, resilient appendageof the conventional clamp 22. It is, of course, also understood that anynumber of secondary clamps 62 can be used, consistent with the need foradequate clearances for wire bonding.

When a semiconductor die 10 and a lead frame strip, including leadfingers 14 of a conventional lead frame, is aligned with the bond sitewindow 60 in the conventional clamp 22 and pressure is exerted on thelead frame, the contact end 63 of the secondary clamp 62 contacts themovable and/or adjustable arm 24 through lead fingers 14 extending fromthe lead frame over the active die surface. The secondary clamp 62 doesnot damage the semiconductor die 10 under the secondary clamp contactend 63 because of the resilient nature of the secondary clamp 62 andbecause of movable and/or adjustable arm 24 positioned between thesemiconductor die 10 and the secondary clamp 62.

The semiconductor die 10 has a conventional lead frame arrangementwherein the lead fingers 14 extend adjacent the upper (active)semiconductor die 10. The bond site window contact lip 65 contacts thelead fingers 14 around the periphery of the semiconductor die 10. Thesecondary clamp 62 extends toward the center of the semiconductor die10. A plurality of wires 16 is then attached between the bond pads ofthe semiconductor die 10 and the lead fingers 14.

The contact end 63 of the secondary clamp 62, in its unbiased statepreferably extends slightly below the bond site window contact lip 65 ofthe bond site window 60 of the conventional clamp 22. The secondaryclamp 62 may be formed from a substantially rigid, non-deformablematerial, such as metal, high-temperature plastic, fiber composites, orthe like. A preferred material for the secondary clamp 62 is 440Cstainless steel.

Referring to drawing FIG. 7, an independently actuated lead clamp 70 isshown in conjunction with the movable and/or adjustable arms 24 in orderto further stabilize the lead fingers during the wire bonding process.Independently actuated lead clamp 70 may be used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 inposition during the bonding process. The conventional clamp 22 helpsensure that the lead finger is in contact with the movable and/oradjustable arm 24 during the bonding process and helps minimize anydeflection of the end 15 of the lead finger 14 so that the bondingapparatus 26 accurately and precisely contacts the end 15 to provide thedesired wire bond. The action of independent actuated lead clamp 70 and,if desired, the additional use of conventional clamp 22, providesimproved clamping of a lead finger 14 during the wire bonding process,as well as ensures that the lead finger 14 of a conventional lead frameis in intimate contact with the movable and/or adjustable arm 24 foreffectiveness.

Independent actuated lead clamp 70 may be of any suitable shape for usein independently clamping the lead finger 14, in place of the use ofconventional clamp 22, such as square, semicircular, rectangular,arcuate, etc. Also, the independent actuated lead clamp 70 may beresiliently mounted through the use of a shoulder 72 thereon, abutting aspring 74, to control the amount of the force exerted on any lead finger14 during the wire bonding operation. If desired, the independentactuated lead clamp 70 may include insulation or cushioning 76 on theend thereof. The independent actuated lead clamp 70 is actuatedindependently of bonding apparatus 26 and has the capability ofindependent movement along the x-axis, y-axis and z-axis with respect tothe bonding apparatus 26. The independent actuated lead clamp 70 is alsofree to move about the bonding apparatus 26 and the central axis of thedie 10 so that any lead finger 14 of a conventional lead frame that isto be connected to bond pads on the die 10, regardless of location, maybe accommodated. The independent actuated lead clamp 70 does not need tobe, and preferably is not, concentrically centered about the bondingapparatus 26 so that it will not interfere with the operation thereof.Any desired number of independent actuated lead clamps 70 may be usedabout the bonding apparatus to minimize the amount of movement of theindependent actuated lead clamp 70 between wire bonding operations. Theindependent actuated lead clamp 70 may be located in quadrants about thedie 10 in any manner as desired.

During the bond operation, one or more of the independent actuated leadclamps 70 clamps the end 15 of lead finger 14 of a conventional leadframe prior to the bonding of a wire 16 thereto by one or more of thebonding apparatus 26. The independent actuated lead clamp 70 appliessufficient pressure to the end 15 of lead finger 14 to press the leadfinger 14 against movable and/or adjustable arm 24 to ensure asatisfactory bond between the end 18 of any wire 16 and the end 15 ofthe lead finger 14.

As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 to the lead finger 14. The bonds of the wire end 18 to theend 15 of the lead finger 14 are typically a wedge type wire bond,although a ball bond may be made, if desired. As shown, the heat block20 is in contact with the paddle 12 and the movable and/or adjustablearm 24, which, in turn, is in contact with the lead fingers 14.

The independent actuated lead clamp 70 may have a modified end or footthereon to provide a larger clamping area of the independent actuatedlead clamp 70 on the end 15 of the lead finger 14 during bondingoperations. The modified end or foot may be substantially the same widthas the lead finger 14 of a conventional lead frame and may be mounted tohave articulated movement about the end of the independent actuated leadclamp 70, such as using a pin extending through suitable apertures in apair of ears attached to the foot.

The independent actuated lead clamp 70 may be integrally attached to theconventional clamp 22 or may have an articulated mounting arrangement.The modified end or foot may be generally semicircular or arcuate inconfiguration, so as to engage a large portion of the end 15 of the leadfinger 14 of a conventional lead frame surrounding the bonding apparatus26 during the wire bonding operation to hold the end 15 in position.

The independent actuated lead clamp 70 may also be used in conjunctionwith a second independently actuated clamp. The second independentlyactuated clamp may be of any suitable type and structure such asdescribed and illustrated hereinbefore. The independent actuated leadclamp 70 and the second clamp may be actuated independently of eachother and independently of the bonding apparatus 26, as described andillustrated hereinbefore.

Referring to drawing FIG. 8, an independently actuated lead clamp 70 isshown having a lead finger penetrating portion 78 on the bottom thereofused in place of or in addition to the conventional clamp 22, tomaintain the lead finger 14 of a conventional lead frame during thebonding process. One or more of the independent actuated lead clamps 70,having lead finger penetrating portions 78 located thereon, contacts andpenetrates the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 to the lead finger 14. The independent actuated lead clamp70, having lead finger penetrating portion 78 thereon, may be of anysuitable shape for use in independently clamping the lead finger 14, inplace of the use of conventional clamp 22, such as square, semicircular,rectangular, arcuate, etc. Also, as shown, the independent actuated leadclamp 70, having lead finger penetrating portion 78 thereon, may beresiliently mounted through the use of a shoulder 72 thereon, abutting aspring 74, to control the amount of force exerted on any lead finger 14during the wire bonding operation. As described hereinbefore, theindependent actuated lead clamp 70, having lead finger penetratingportion 78 thereon, is actuated independently of bonding apparatus 26and has the capability of independent movement along the x-axis, y-axisand z-axis with respect to the bonding apparatus 26. The independentactuated lead clamp 70, having lead finger penetrating portion 78thereon, is also free to move about the bonding apparatus 26 and thecentral axis of the die 10, so that any lead finger 14 of a conventionallead frame that is to be connected to a bond pad on the die 10,regardless of location, may be accommodated. The independent actuatedlead clamp 70, having lead finger penetrating portion 78 thereon, doesnot need to be, and preferably is not, concentrically centered about thebonding apparatus 26, so that it will not interfere with the operationthereof. Any desired number of independent actuated lead clamps 70,having lead finger penetrating portion 78 thereon, may be used about thebonding apparatus to minimize the amount of movement of the independentactuated lead clamp 70 between wire bonding operations. Also, theindependent actuated lead clamps 70 may be located in quadrants aboutthe die 10, or in any manner as desired.

The independently actuated lead clamp 70 has a lead finger penetratingportion 78 on the bottom thereof used in place of or in addition to theconventional clamp 22 to maintain the lead finger 14 in position duringthe bonding process. Such independent actuated lead clamp 70 helpsensure that the lead finger 14 is in contact with the movable and/oradjustable arm 24 during the bonding process, immobilizes the leadfinger 14 during the wire bonding process, and helps minimize anydeflection of the end 15 of the lead finger 14 so that the bondingapparatus 26 accurately and precisely contacts the end 15 to provide thedesired wire bond. The action of such independent actuated lead clamp 70and, if desired, the additional use of conventional clamp 22, providesimproved clamping and immobilization of a lead finger 14 during the wirebonding process, as well as ensures that the lead finger 14 is inintimate contact with the movable and/or adjustable arm 24 foreffectiveness.

During the wire bonding process, it is desirable for the heat block 20to be heated, as previously described hereinbefore. Similarly, thebonding apparatus 26 should exert substantially the same amount offorce, as described hereinbefore.

During the bond operation, one or more of the independent actuated leadclamps 70, having a lead finger penetrating portion 78 located on theend thereof, clamps the end 15 of lead finger 14 prior to the bonding ofa wire 16 thereto by one or more of the bonding apparatus 26. Theindependent actuated lead clamp 70 applies sufficient pressure to theend 15 of the lead finger 14 to ensure a satisfactory bond between theend of any wire 16 and the end 15 of the lead finger 14.

As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 to the lead finger 14. The bonds of the wire end 18 to theend 15 of the lead finger 14 are typically a wedge type wire bond,although a ball bond may be made if, desired. As shown, the heat block20 is in contact with the paddle 12 of the lead frame. The lead fingers14 of a conventional lead frame are in contact with the movable and/oradjustable arm 24 which, in turn, is in contact with the heat block 20.

As also shown, the conventional clamps 22 are formed to have apenetrating portion 80 thereon which penetrates the end 15 of leadfinger 14 of a conventional lead frame. In this manner, the conventionalclamp 22 provides improved clamping and immobilization of a lead finger14 during the wire bonding process, as well as ensures that the leadfinger 14 is in intimate contact with the movable and/or adjustable arm24 for effectiveness. As shown, the clamps 22 and 70 having lead fingerpenetrating portions thereon cause the lead finger 14 to engage themovable and/or adjustable arm 24 with the movable and/or adjustable armbeing in contact with the heat block 20. However, care should be takento prevent the lead finger penetrating portion 78 of the independentactuated lead clamp 70 from either damaging the lead finger 14,affecting its electrical characteristics, or severing the lead finger14.

The independent actuated lead clamp 70 may be formed having a modifiedend or foot thereon to provide a larger clamping area of the independentactuated lead clamp 70 on the end 15 of the lead finger 14 duringbonding operations. The modified end or foot is substantially the samewidth as the lead finger 14 and may be mounted to have articulatedmovement about the end of the independent actuated lead clamp 70, suchas using a pin extending through suitable apertures in a pair of earsattached to the foot and the end of the modified independent actuatedlead clamp 70. Located on the bottom of the modified end or foot of theindependent actuated lead clamp 70 are suitable lead finger penetratingmembers which penetrate the lead finger 14 to immobilize it during wirebonding operations as described hereinbefore. The lead fingerpenetrating portion 78 may comprise a plurality of round shaped memberslocated to either extend along the axis of a lead finger 14 or extendtransversely thereof or may comprise a knife edge shape extendingtransversely across the axis of a lead finger 14. The shapes are to bemerely illustrative of a variety of shapes for the lead fingerpenetrating portion 78, which may be used. The modified end or foot maybe semicircular or arcuate in configuration so as to engage a largeportion of the end 15 of the lead finger 14 surrounding the bondingapparatus 26 during the wire bonding operation to hold the end 15 inposition. Also, a soft metal coating located on the lead finger 14 maybe penetrated by either the independent actuated lead clamp 70 or theconventional clamp 22. The soft metal coating applied to the lead finger14 may be of any suitable type, such as gold, silver, aluminum, etc.,which will allow for the easy penetration of the coating by a portion ofeither the independent actuated lead clamp 70 or the conventional clamp22. The independent actuated lead clamp 70 may act on the opposite sideof the conventional clamp 22 from the bonding apparatus 26. It should beunderstood that any of the penetrating clamps, hereinbefore described,may act on the opposite side of the conventional clamp 22 during thewire bonding operations regarding a lead finger 14. It is not necessarythat the penetrating clamp be positioned on the same side of the leadfinger 14 as the bonding apparatus 26.

Referring to drawing FIG. 9, a semiconductor device (die) 10 is shown inrelation to a leads-over-chip (LOC) lead frame without being supporteddirectly by adhesive connection to the lead fingers 14 of the leadframe. (Note, that as shown in FIGS. 9 through 14, the die 10 issupported only by the wire 16 between the bond pads on the die 10 andthe lead fingers 14.) A heat block 20 is used to heat the die 10 duringthe wire bonding process. As shown, a suitable wire 16, as describedhereinbefore, has one end 17 thereof bonded to a bond pad of the die 10.The wire 16 may be of any suitable type for connection and bondingpurposes, such as gold, gold alloy, aluminum, aluminum alloy, etc. Theother end 18 of the wire 16 is shown being bonded to the end 15 of alead finger 14 of the lead frame by a suitable bonding apparatus 26. Thebonding apparatus 26 may be of any suitable type well known in thebonding area, such as described hereinbefore. If desired, in the wirebonding operation, further shown in contact with lead finger 14, is aportion of a conventional clamp 22 used to clamp portions of the leadframe during such bonding operations. The conventional clamp 22 may beof any well known suitable type, such as those described hereinbefore,and is generic in shape. Further shown in drawing FIG. 9 is movableand/or adjustable arm 24, having a lead support portion 25, attached toor an integral part of the movable and/or adjustable arm 24. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned between the die 10and the lead fingers 14 of the LOC lead frame. The movable and/oradjustable arm 24 and lead support portion 25 thus substantially preventthe application of any force against the die 10 from the bondingapparatus 26 and the conventional clamp 22. In addition, movable and/oradjustable arm 24 and lead support portion 25 conduct heat from the heatblock 20 to the lead fingers 14. The action of movable and/or adjustablearm 24 and lead support portion 25 provides improved support of a leadfinger 14 during the wire bonding process, as well as ensures that theforce applied by bonding apparatus 26 and conventional clamp 22 issubstantially against lead support portion 25 and movable and/oradjustable arm 24 rather than against the die 10. After the bonding ofthe wire 16 to the lead fingers 14 of the LOC lead frame, the wires 16support the die 10 during subsequent molding operations to encapsulatethe die 10 and a portion of the LOC lead frame.

The movement of the movable and/or adjustable arm 24 may be effectuatedby various means 28, such as described hereinbefore.

The movable and/or adjustable arm 24 is dynamically attached to the heatblock 20 so that as the heat block moves into position during the wirebonding process, the movable and/or adjustable arm and lead supportportion 25 move into position between the lead fingers 14 and the die10. As shown, movable and/or adjustable arm 24 is shown as travelingagainst the heat block 20 such that the direction of travel issubstantially parallel with respect to the lower surface 19 of the leadfingers 14 of a LOC lead frame.

Referring to drawing FIG. 10, movable and/or adjustable arm 24 may beattached to heat block 20 such that the direction of travel, withrespect to lower surface 19 of lead fingers 14 of a LOC lead frame, isangular or arcuate. A radius 54 may be formed in heat block 20 andmovable and/or adjustable arm 24 such that the direction of travel oflead support portion 25 and movable and/or adjustable arm 24 is arcuate,with respect to lower surface 19 of the lead fingers 14 of aconventional lead frame, as the lead support portion is positioned priorto wire bonding.

Referring to drawing FIG. 11, the surface of the heat block 20 andmovable and/or adjustable arm 24 may also be angled 56, with respect tolower surface 19 of the lead fingers 14 of a LOC lead frame, such thatthe direction of travel of lead support portion 25 and movable and/oradjustable arm 24 is angular, with respect to lower surface 19 of leadfingers 14 of a LOC lead frame, as the lead support portion and movablearm are positioned prior to the wire bonding process.

The movement of the movable and/or adjustable arm 24 and the heat block20 may be integrated so that as the heat block moves into position itcauses the movable arm to move into position. As shown, notch 50 isformed in movable and/or adjustable arm 24 and extends into a slot 52formed in a stationary member (not shown). Thus, as the heat block 20moves upward to contact the die 10, the heat block pushes against themovable and/or adjustable arm 24, which is forced to travel upward andinward by the notch 50, traveling in the slot 52.

Referring to drawing FIG. 12, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers 14 of a LOC lead frame during thewire bonding process. The conventional clamp 22 acts as a primary clampand includes a bond site window 60. The bond site window 60 is sized toallow access for a bonding apparatus 26 to a plurality of bond pads ofsemiconductor die 10 and to a plurality of lead fingers 14 of aconventional lead frame.

The bond site window 60 includes a secondary clamp 62. The secondaryclamp 62 has the same construction and operation as has been describedhereinbefore.

The semiconductor die 10 has a LOC lead frame arrangement wherein thelead fingers 14 extend over the upper (active) semiconductor die 10. Thebond site window contact lip 65 contacts the lead fingers 14 of the LOClead frame around the periphery of the semiconductor die 10. Thesecondary clamp 62 extends toward the center of the semiconductor die10. A plurality of wires 16 is then attached between the bond pads ofthe semiconductor die 10 and the lead fingers 14.

The contact end 63 of the secondary clamp 62 in its unbiased statepreferably extends slightly below a bond site window contact lip 65 ofthe bond site window 60 of the conventional clamp 22.

Referring to drawing FIG. 13, an independently actuated lead clamp 70 isshown in conjunction with the movable and/or adjustable arms 24 in orderto further stabilize the lead fingers 14 of a LOC lead frame during thewire bonding process. Independently actuated lead clamp 70 may be usedin place of or in addition to the conventional clamp 22 to maintain thelead finger 14 in position during the bonding process. The conventionalclamp 22 is the same as hereinbefore described in construction andoperation to help ensure that the lead finger is in contact with themovable and/or adjustable arm 24 during the bonding process and helpsminimize any deflection of the end 15 of the lead finger 14 so that thebonding apparatus 26 accurately and precisely contacts the end 15 toprovide the desired wire bond. The action of independent actuated leadclamp 70 and, if desired, the additional use of conventional clamp 22,provides improved clamping of a lead finger 14 during the wire bondingprocess, as well as ensures that the lead finger 14 of a conventionallead frame is in intimate contact with the movable and/or adjustable arm24 for effectiveness.

Referring to drawing FIG. 14, as described hereinbefore, anindependently actuated lead clamp 70 is shown having a lead fingerpenetrating portion 78 on the bottom thereof, used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 ofa LOC lead frame during the bonding process. One or more of theindependent actuated lead clamp 70, having lead finger penetratingportions 78 located thereon contacts and penetrates the end 15 of leadfinger 14 aft of the area of the bond of wire end 18 to the lead finger14.

Referring to drawing FIG. 15, a semiconductor device (die) 10 is shownin relation to a leads-over-chip (LOC) lead frame being supporteddirectly by adhesive attachment through adhesive coatings 1 on the tape2 to the lead fingers 14 on the lead frame. (Also, note that as shown inFIGS. 15 through 20, a die 10 is shown in relation to a LOC lead framebeing supported directly by adhesive attachment through adhesivecoatings 1 on the tape 2 to the lead fingers 14 on the lead frame.) Aheat block 20 is used to heat the die 10 during the wire bondingprocess. As shown, a suitable wire 16, as described hereinbefore, hasone end 17 thereof bonded to a bond pad of the die 10. The other end 18of the wire 16 is shown being bonded to the end 15 of a lead finger 14of the lead frame by a suitable bonding apparatus 26. The bondingapparatus 26 may be of any suitable type well known in the bonding area,as described hereinbefore. If desired, in the wire bonding operation,further shown in contact with lead finger 14, is a portion of aconventional clamp 22 used to clamp portions of the lead frame duringsuch bonding operations. The conventional clamp 22 may be of any wellknown suitable type, such as those described hereinbefore, and isgeneric in shape. Further shown in drawing FIG. 15 is movable and/oradjustable arm 24, having a lead support portion 25, attached to or anintegral part of the movable and/or adjustable arm 24. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned between the die 10and the lead fingers 14 of the LOC lead frame. The movable and/oradjustable arm 24 and lead support portion 25 thus substantially preventthe application of any force against the die 10 from the bondingapparatus 26 and the conventional clamp 22. In addition, movable and/oradjustable arm 24 and lead support portion 25 conduct heat from the heatblock 20 to the lead fingers 14. The action of movable and/or adjustablearm 24 and lead support portion 25 provides improved support of a leadfinger 14 during the wire bonding process, as well as ensures that theforce applied by bonding apparatus 26 and conventional clamp 22 issubstantially against lead support portion 25 and movable and/oradjustable arm 24, rather than against the die 10. During subsequentmolding operations to encapsulate the die 10, a portion of the LOC leadframe of the die 10 is supported by the lead fingers 14 of the LOC leadframe through the adhesive coatings 1 and tape 2.

The movement of the movable and/or adjustable arm 24 may be effectuatedby various means 28, as described hereinbefore.

The movable and/or adjustable arm 24 is dynamically attached to the heatblock 20 so that as the heat block moves into position during the wirebonding process, the movable and/or adjustable arm 24 and lead supportportion 25 move into position between the lead fingers 14 and the die10. The movable and/or adjustable arm 24 is shown as traveling againstthe heat block 20 such that the direction of travel is substantiallyparallel with respect to the lower surface 19 of the lead fingers 14 ofa LOC lead frame.

Referring to drawing FIG. 17, movable and/or adjustable arm 24 may beattached to heat block 20, such that the direction of travel, withrespect to lower surface 19 of lead fingers 14 of a LOC lead frame, isangular or arcuate. A radius 54 may be formed in heat block 20 andmovable and/or adjustable arm 24, such that the direction of travel oflead support portion 25 and movable and/or adjustable arm 24 is arcuate,with respect to lower surface 19 of the lead fingers 14 of aconventional lead frame, as the lead support portion is positioned priorto wire bonding.

Referring to drawing FIG. 16, the surface of the heat block 20 andmovable and/or adjustable arm 24 may also be angled 56, with respect tolower surface 19 of the lead fingers 14 of a LOC lead frame, such thatthe direction of travel of lead support portion 25 and movable and/oradjustable arm 24 is angular, with respect to lower surface 19 of leadfingers 14 of a LOC lead frame, as the lead support portion 25 andmovable and/or adjustable arm 24 are positioned prior to the wirebonding process.

The movement of the movable and/or adjustable arm 24 and the heat block20 may be integrated so that as the heat block moves into position itcauses the movable and/or adjustable arm to move into position. In FIG.16, a notch 50 is shown formed in movable and/or adjustable arm 24 andextends into a slot 52 formed in a stationary member (not shown). Thus,as the heat block 20 moves upward to contact the die 10, the heat blockpushes against the movable and/or adjustable arm 24, which is forced totravel upward and inward by the notch 50 traveling in the slot 52.

Referring to drawing FIG. 18, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers 14 of a LOC lead frame during thewire bonding process. The conventional clamp 22 acts as a primary clampand includes a bond site window 60. The bond site window 60 is sized toallow access for a bonding apparatus 26 to a plurality of bond pads ofsemiconductor die 10 and to a plurality of lead fingers 14 of aconventional lead frame.

The bond site window 60 includes a secondary clamp 62. The secondaryclamp 62 is mounted to a resilient plate 64 with a first set screw orbolt 66. The proximal end of each resilient plate 64 is attached to theconventional clamp 22 with a second set screw or bolt 68. It is, ofcourse, understood that secondary clamp 62 can be attached to theconventional clamp 22 in any number of known configurations, includingforming the secondary clamp 62 with an integral resilient portion whichis secured to the conventional clamp 22 or forming (for example, as bymachining) the secondary clamp 62 as an integrated, resilient appendageof the conventional clamp 22. It is, of course, also understood that anynumber of secondary clamps 62 can be used, consistent with the need foradequate clearances for wire bonding.

As described hereinbefore, when a semiconductor die 10 and a lead framestrip, including lead fingers 14 of a LOC lead frame, are aligned withthe bond site window 60 in the conventional clamp 22 and pressure isexerted on the lead frame, the contact end 63 of the secondary clamp 62contacts the movable and/or adjustable arm 24 through lead fingers 14extending from the lead frame over the active die surface. The secondaryclamp 62 does not damage the semiconductor die 10 under the secondaryclamp contact end 63 because of the resilient nature of the secondaryclamp 62 and because of movable and/or adjustable arm 24 positionedbetween the semiconductor die 10 and the secondary clamp 62.

The semiconductor die 10 has a LOC lead frame arrangement wherein thelead fingers 14 extend over the upper (active) semiconductor die 10. Thebond site window contact lip 65 contacts the lead fingers 14 of the LOClead frame around the periphery of the semiconductor die 10. Thesecondary clamp 62 extends toward the center of the semiconductor die10. A plurality of wires 16 is then attached between the bond pads ofthe semiconductor die 10 and the lead fingers 14.

The contact end 63 of the secondary clamp 62, in its unbiased state,preferably extends slightly below a bond site window contact lip 65 ofthe bond site window 60 of the conventional clamp 22. The secondaryclamp 62 may be formed from a substantially rigid, non-deformablematerial such as metal, high-temperature plastic, fiber composites, orthe like. A preferred material for the secondary clamp 62 is 440Cstainless steel.

Referring to drawing FIG. 19, an independently actuated lead clamp 70 isshown in conjunction with the movable and/or adjustable arms 24 in orderto further stabilize the lead fingers 14 of a LOC lead frame during thewire bonding process. Independently actuated lead clamp 70 may be usedin place of or in addition to the conventional clamp 22 to maintain thelead finger 14 in position during the bonding process. The conventionalclamp 22 is the same as hereinbefore described in structure andoperation to help ensure that the lead finger is in contact with themovable and/or adjustable arm 24 during the bonding process and helpsminimize any deflection of the end 15 of the lead finger 14 so that thebonding apparatus 26 accurately and precisely contacts the end 15 toprovide the desired wire bond. The action of independent actuated leadclamp 70 and, if desired, the additional use of conventional clamp 22,provides improved clamping of a lead finger 14 during the wire bondingprocess, as well as ensures that the lead finger 14 of a conventionallead frame is in intimate contact with the movable and/or adjustable arm24 for effectiveness.

Referring to drawing FIG. 20, as described hereinbefore, anindependently actuated lead clamp 70 is shown, having a lead fingerpenetrating portion 78 on the bottom thereof, used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 ofa LOC lead frame during the bonding process. One or more of theindependent actuated lead clamps 70, having lead finger penetratingportions 78 located thereon, contacts and penetrates the end 15 of leadfinger 14 aft of the area of the bond of wire end 18 to the lead finger14. The independent actuated lead clamp 70, having lead fingerpenetrating portion 78 thereon, may be of any suitable shape for use inindependently clamping the lead finger 14, in place of the use ofconventional clamp 22. Also, as shown, the independent actuated leadclamp 70, having lead finger penetrating portion 78 thereon, may beresiliently mounted through the use of a shoulder 72 thereon, abutting aspring 74, to control the amount of force exerted on any lead finger 14during the wire bonding operation.

Referring to drawing FIG. 21, a semiconductor device (die) 10 is shownbeing supported by the paddle 12 of a two piece lead frame, such asdescribed in U.S. Pat. No. 4,984,059. A heat block 20 is used to heatthe paddle 12 and die 10 during the wire bonding process. As shown, asuitable wire 16, such as described hereinbefore, has one end 17 thereofbonded to a bond pad of the die 10. The other end 18 of the wire 16 isshown being bonded to the end 15 of a lead finger 14 of the lead frameby a suitable bonding apparatus 26. The bonding apparatus 26 may be ofany suitable type well known in the bonding area, such as describedhereinbefore. If desired, in the wire bonding operation, further shownin contact with lead finger 14, is a portion of a conventional clamp 22used to clamp portions of the lead frame during such bonding operations.The conventional clamp 22 may be of any well known suitable type, suchas those described hereinbefore, and is generic in shape. Further, shownin drawing FIG. 21, is movable and/or adjustable arm 24, having a leadsupport portion 25, attached to or an integral part of the movableand/or adjustable arm 24. The movable and/or adjustable arm 24 isdynamically attached to the heat block 20 so that the lead supportportion 25 can be positioned between the die 10 and the lead fingers 14.The movable and/or adjustable arm 24 and lead support portion 25 thussubstantially prevent the application of any force against the die 10from the bonding apparatus 26 and the conventional clamp 22. Inaddition, movable and/or adjustable arm 24 and lead support portion 25conduct heat from the heat block 20 to the lead fingers 14. The actionof movable and/or adjustable arm 24 and lead support portion 25 providesimproved support of a lead finger 14 during the wire bonding process, aswell as ensures that the force applied by bonding apparatus 26 andconventional clamp 22 is substantially against lead support portion 25and movable and/or adjustable arm 24, rather than against the die 10.

The movement of the movable and/or adjustable arm 24 may be effectuatedby various means 28, such as described hereinbefore.

The movable and/or adjustable arm 24 is dynamically attached to the heatblock 20 so that as the heat block moves into position during the wirebonding process, the movable and/or adjustable arm 24 and lead supportportion 25 move into position between the lead fingers 14 and the die10. The movable and/or adjustable arm 24 is shown as traveling againstthe heat block 20, such that the direction of travel is substantiallyparallel with respect to the lower surface 19 of the lead fingers 14 ofa conventional lead frame.

Referring to drawing FIG. 22, movable and/or adjustable arm 24 may beattached to heat block 20, such that the direction of travel withrespect to lower surface 19 of lead fingers 14 is angular or arcuate. Aradius 54 may be formed in heat block 20 and movable and/or adjustablearm 24, such that the direction of travel of lead support portion 25 andmovable and/or adjustable arm 24 is arcuate, with respect to lowersurface 19 of the lead fingers 14 of a conventional lead frame, as thelead support portion 25 is positioned prior to wire bonding.

Referring to drawing FIG. 23, the surface of the heat block 20 andmovable and/or adjustable arm 24 may also be angled 56, with respect tolower surface 19 of the lead fingers 14, such that the direction oftravel of lead support portion 25 and movable and/or adjustable arm 24is angular, with respect to lower surface 19 of lead fingers 14, as thelead support portion 25 and movable and/or adjustable arm 24 arepositioned prior to the wire bonding process.

The movement of the movable and/or adjustable arm 24 and the heat block20 may be integrated so that as the heat block moves into position itcauses the movable and/or adjustable arm to move into position. In FIG.23, a notch 50 is shown formed in movable and/or adjustable arm 24 andextends into a slot 52 formed in a stationary member (not shown). Thus,as the heat block 20 moves upward to contact the die 10, the heat blockpushes against the movable and/or adjustable arm 24, which is forced totravel upward and inward by the notch 50 traveling in the slot 52.

Referring to drawing FIG. 24, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers during the wire bonding process. Theconventional clamp 22 acts as a primary clamp and includes a bond sitewindow 60. The bond site window 60 is sized to allow access for abonding apparatus 26 to a plurality of bond pads of semiconductor die 10and to a plurality of lead fingers 14 of a conventional lead frame.

The bond site window 60 includes a secondary clamp 62, the same inconstruction and operation as described hereinbefore. The secondaryclamp 62 is mounted to a resilient plate 64 with a first set screw orbolt 66. The proximal end of each resilient plate 64 is attached to theconventional clamp 22 with a second set screw or bolt 68. It is, ofcourse, understood that secondary clamp 62 can be attached to theconventional clamp 22 in any number of known configurations, includingforming the secondary clamp 62 with an integral resilient portion whichis secured to the conventional clamp 22 or forming (for example, as bymachining) the secondary clamp 62 as an integrated, resilient appendageof the conventional clamp 22. It is, of course, also understood that anynumber of secondary clamps 62 can be used, consistent with the need foradequate clearances for wire bonding.

When a semiconductor die 10 and a lead frame strip, including leadfingers 14 of a two piece lead frame, is aligned with the bond sitewindow 60 in the conventional clamp 22 and pressure is exerted on thelead frame, the contact end 63 of the secondary clamp 62 contacts themovable and/or adjustable arm 24 through lead fingers 14 extending fromthe lead frame over the active die surface. The secondary clamp 62 doesnot damage the semiconductor die 10 under the secondary clamp contactend 63 because of the resilient nature of the secondary clamp 62 andbecause of movable and/or adjustable arm 24 positioned between thesemiconductor die 10 and the secondary clamp 62.

The semiconductor die 10 has a two piece lead frame arrangement whereinthe lead fingers 14 extend over the upper (active) semiconductor die 10.The bond site window contact lip 65 contacts the lead fingers 14 aroundthe periphery of the semiconductor die 10. The secondary clamp 62extends toward the center of the semiconductor die 10. A plurality ofwires 16 is then attached between the bond pads of the semiconductor die10 and the lead fingers 14.

The contact end 63 of the secondary clamp 62 in its unbiased state,preferably extends slightly below bond site window contact lip 65 of thebond site window 60 of the conventional clamp 22.

Referring to drawing FIG. 25, an independently actuated lead clamp 70,such as described hereinbefore, is shown in conjunction with the movableand/or adjustable arms 24 in order to further stabilize the lead fingers14 of a two piece lead frame during the wire bonding process.Independently actuated lead clamp 70 may be used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 inposition during the bonding process. The conventional clamp 22 helpsensure that the lead finger is in contact with the movable and/oradjustable arm 24 during the bonding process and helps minimize anydeflection of the end 15 of the lead finger 14, so that the bondingapparatus 26 accurately and precisely contacts the end 15 to provide thedesired wire bond. The action of independent actuated lead clamp 70 and,if desired, the additional use of conventional clamp 22, providesimproved clamping of a lead finger 14 during the wire bonding process,as well as ensures that the lead finger 14 of a two piece lead frame isin intimate contact with the movable and/or adjustable arm 24 foreffectiveness.

Independent actuated lead clamp 70 may be of any suitable shape for usein independently clamping the lead finger 14, in place of the use ofconventional clamp 22. Also, the independent actuated lead clamp 70 maybe resiliently mounted through the use of a shoulder 72 thereon,abutting a spring 74, to control the amount of force exerted on any leadfinger 14 during the wire bonding operation. If desired, the independentactuated lead clamp 70 may include insulation or cushioning 76 on theend thereof.

During the bond operation, one or more of the independent actuated leadclamps 70 clamps the end 15 of lead finger 14 of a two piece lead frameprior to the bonding of a wire 16 thereto by one or more of the bondingapparatus 26. The independent actuated lead clamp 70 applies sufficientpressure to the end 15 of lead finger 14 to press the lead finger 14against movable and/or adjustable arm 24 to ensure a satisfactory bondbetween the end 18 of any wire 16 and the end 15 of the lead finger 14.

As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end lead finger 14. The bonds of the wire end 18 to the end 15 ofthe lead finger 14 are typically a wedge type wire bond, although a ballbond may be made if desired. As shown, the heat block 20 is in contactwith the paddle 12 and the movable and/or adjustable arm 24, which, inturn, is in contact with the lead fingers 14.

The independent actuated lead clamp 70 may have a modified end or footthereon to provide a larger clamping area of the independent actuatedlead clamp 70 on the end 15 of the lead finger 14 during bondingoperations. The modified end or foot may be substantially the same widthas the lead finger 14 of a conventional lead frame and may be mounted tohave articulated movement about the end of the independent actuated leadclamp 70, such as using a pin extending through suitable apertures in apair of ears attached to the foot.

The independent actuated lead clamp 70 may be integrally attached to theconventional clamp 22 or may have an articulated mounting arrangement.The modified end or foot may be generally semicircular, or arcuate, inconfiguration so as to engage a large portion of the end 15 of the leadfinger 14 of a conventional lead frame surrounding the bonding apparatus26 during the wire bonding operation to hold the end 15 in position.

The independent actuated lead clamp 70 may also be used in conjunctionwith a second independently actuated clamp. The second independentlyactuated clamp may be of any suitable type and structure, such asdescribed and illustrated hereinbefore. The independent actuated leadclamp 70 and the second clamp may be actuated independently of eachother and independently of the bonding apparatus 26, as described andillustrated hereinbefore.

Referring to drawing FIG. 26, an independently actuated lead clamp 70,such as described hereinbefore, is shown, having a lead fingerpenetrating portion 78 on the bottom thereof, used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 ofa two-piece lead frame during the bonding process. One or more of theindependent actuated lead clamps 70, having lead finger penetratingportions 78 located thereon, contacts and penetrates the end 15 of leadfinger 14 aft of the area of the bond of wire end 18 bonded to the leadfinger 14. The independent actuated lead clamp 70, having lead fingerpenetrating portion 78 thereon, may be of any suitable shape for use inindependently clamping the lead finger 14, in place of the use ofconventional clamp 22. Also, as shown, the independent actuated leadclamp 70, having lead finger penetrating portion 78 thereon, may beresiliently mounted through the use of a shoulder 72 thereon, abutting aspring 74, to control the amount of force exerted on any lead finger 14during the wire bonding operation. As described hereinbefore, theindependent actuated lead clamp 70, having lead finger penetratingportion 78 thereon, is actuated independently of bonding apparatus 26and has the capability of independent movement along the x-axis, y-axisand z-axis with respect to the bonding apparatus 26. The independentactuated lead clamp 70, having lead finger penetrating portion 78thereon, is also free to move about the bonding apparatus 26 and thecentral axis of the die 10, so that any lead finger 14 of a conventionallead frame that is to be connected to a bond pad on the die 10,regardless of location, may be accommodated. The independent actuatedlead clamp 70, having lead finger penetrating portion 78 thereon, doesnot need to be, and preferably is not, concentrically centered about thebonding apparatus 26, so that it will not interfere with the operationthereof. Any desired number of independent actuated lead clamps 70,having lead finger penetrating portion 78 thereon, may be used about thebonding apparatus 26 to minimize the amount of movement of theindependent actuated lead clamp 70 between wire bonding operations.Also, the independent actuated lead clamps 70 may be located inquadrants about the die 10, or in any manner as desired.

The independently actuated lead clamp 70 has a lead finger penetratingportion 78 on the bottom thereof used in place of or in addition to theconventional clamp 22 to maintain the lead finger 14 in position duringthe bonding process. Such independent actuated lead clamp 70 helpsensure that the lead finger 14 is in contact with the movable and/oradjustable arm 24 during the bonding process, immobilizes the leadfinger 14 during the wire bonding process, and helps minimize anydeflection of the end 15 of the lead finger 14 so that the bondingapparatus 26 accurately and precisely contacts the end 15 to provide thedesired wire bond. The action of such independent actuated lead clamp 70and, if desired, the additional use of conventional clamp 22, providesimproved clamping and immobilization of a lead finger 14 during the wirebonding process, as well as ensures that the lead finger 14 is inintimate contact with the movable and/or adjustable arm 24 foreffectiveness.

During the wire bonding process, it is desirable for the heat block 20to be heated, as previously described hereinbefore. Similarly, thebonding apparatus 26 should exert substantially the same amount offorce, as described hereinbefore.

During the bond operation, one or more of the independent actuated leadclamps 70, having a lead finger penetrating portion 78 located on theend thereof, clamps the end 15 of lead finger 14 prior to the bonding ofa wire 16 thereto by one or more of the bonding apparatus 26. Theindependent actuated lead clamp 70 applies sufficient pressure to theend 15 of the lead finger 14 to ensure a satisfactory bond between theend of any wire 16 and the end 15 of the lead finger 14.

As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 bonded to the lead finger 14. The bonds of the wire end 18to the end 15 of the lead finger 14 are typically a wedge type wirebond, although a ball bond may be made if desired. As shown, the heatblock 20 is in contact with the paddle 12 of the lead frame. The leadfingers 14 of a two piece lead frame are in contact with the movableand/or adjustable arm 24 which, in turn, is in contact with the heatblock 20.

As also shown, the conventional clamps 22 are formed to have apenetrating portion 80 thereon, which penetrates the end 15 of leadfinger 14 of a conventional lead frame. In this manner, the conventionalclamp 22 provides improved clamping and immobilization of a lead finger14 during the wire bonding process, as well as ensures that the leadfinger 14 is in intimate contact with the movable and/or adjustable arm24 for effectiveness. As shown, the clamps 22 and 70, having lead fingerpenetrating portions 78 and 80 thereon, cause the lead finger 14 toengage the movable and/or adjustable arm 24 with the movable and/oradjustable arm 24 being in contact with the heat block 20. However, careshould be taken to prevent the lead finger penetrating portion 78 of theindependent actuated lead clamp 70 from either damaging the lead finger14, affecting its electrical characteristics, or severing the leadfinger 14.

The independent actuated lead clamp 70 may be formed having a modifiedend or foot thereon, to provide a larger clamping area of theindependent actuated lead clamp 70 on the end 15 of the lead finger 14during bonding operations, as described hereinbefore. It should beunderstood that any of the penetrating clamps, hereinbefore described,may act on the opposite side of the conventional clamp 22 during thewire bonding operations regarding a lead finger 14. It is not necessarythat the penetrating clamp be positioned on the same side of the leadfinger 14 as the bonding apparatus 26.

Referring to drawing FIG. 27, a semiconductor device (die) 10 is shownbeing supported by the paddle 12 of a hybrid lead frame having leadfingers 14 located on differing levels with respect to the semiconductordevice 10. That is, a portion of the lead fingers is located on a firstlevel with respect to the lead frame and another portion of the leadfingers is located on a second level with respect to the lead frame. Thelower portion of the lead fingers 14 of the lead frame are supported byheat block 20 during the bonding operation while the other portion oflead fingers 14 is supported by the lead support portion 25 of movableand/or adjustable arm 24 (not shown) during the wire bonding operations.A heat block 20 is used to heat the paddle 12 and die 10 during the wirebonding process. As shown, a suitable wire 16, such as describedhereinbefore, has one end 17 thereof bonded to a bond pad of the die 10.The wire 16 may be of any suitable type for connection and bondingpurposes as, described hereinbefore. The other end 18 of the wire 16 isshown being bonded to the end 15 of a lead finger 14 of the lead frameby a suitable bonding apparatus 26. The bonding apparatus 26 may be ofany suitable type well known in the bonding area, as describedhereinbefore. If desired, in the wire bonding operation, further shownin contact with lead finger 14 is a portion of a conventional clamp 22used to clamp portions of the lead frame during such bonding operations.The conventional clamp 22 may be of any well known suitable type, suchas those described hereinbefore, and is generic in shape. As shown indrawing FIG. 28, movable and/or adjustable arm 24, having a lead supportportion 25, is attached to or an integral part thereof. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned under a portion ofthe lead fingers 14. The movable and/or adjustable arm 24 and leadsupport portion 25 thus allow for improved wire bonding to the elevatedlead fingers 14 of the hybrid lead frame. In addition, movable and/oradjustable arm 24, having lead support portion 25, conducts heat fromthe heat block 20 to the lead fingers 14.

The movement of the movable and/or adjustable arm 24 may be effectuatedby various means 28, such as described hereinbefore. The movable and/oradjustable arm 24 is dynamically attached to the heat block 20 so thatas the heat block moves into position during the wire bonding process,the movable and/or adjustable arm 24, having lead support portion 25,moves into position under a portion of the lead fingers 14.

Referring to drawing FIG. 28, the movable and/or adjustable arm 24 isshown in relation to the semiconductor device 10 and lead fingers 14 ofthe hybrid lead frame. As illustrated, the heat block 20 supports thelower level or first portion of lead fingers 14 during wire bondingoperations while the lead support portion 25 of the movable and/oradjustable arm 24 supports the upper level or other portion of the leadfingers 14 during wire bonding operations by bonding apparatus 26.

METHOD OF BONDING

Referring to drawing FIGS. 1, 4 and 5, in the method of the presentinvention, a die 10 is positioned within the bonding area of the bondingapparatus 26. A movable and/or adjustable arm 24 having a lead supportportion 25, is positioned such that the lead support portion 25 isbetween the die 10 and the lead fingers 14. A conventional clamp 22serves to help straighten the lead frame and position the lead fingers14 during subsequent bonding operations. Next, the die 10 and the leadfingers 14 are heated to the desired temperature before bondingoperations by the heat block 20 acting through movable and/or adjustablearm 24. The bonding apparatus 26 is then actuated to form a wire bond onend 17 of wire 16 to an appropriate bond pad on die 10. After theformation of the bond of end 17 of wire 16 to the bond pad of die 10,the bonding apparatus is moved to appropriate end 15 of lead finger 14for the formation of a suitable wire bond thereto by end 18 of wire 16.During this process, lead support portion 25 of movable and/oradjustable arm 24 acts to substantially oppose the application of forcefrom the bonding apparatus 26 and conventional clamp 22 and to stabilizethe lead fingers 14. After the wire 16 has been bonded to the desiredbond pad of die 10 and end 15 of lead finger 14, the process is repeateduntil all desired wire bonds between lead fingers 14 and bond pads ofdie 10 are completed.

Referring to drawing FIG. 6, if desired to have additional clamping ofthe lead finger 14, a secondary clamp 62 and a conventional clamp 22 maybe used with the bonding apparatus 26. The secondary clamp 62 may beactuated and moved from the lead finger 14 with, before, or after theremoval of the bonding apparatus 26 from the lead finger.

Referring to drawing FIG. 7, if desired to have additional clamping ofthe lead finger 14, either a conventional clamp 22 and/or a secondindependent actuated lead clamp 70 may be used with the bondingapparatus 26. The second independent actuated lead clamp 70 may beactuated and moved from the lead finger 14 with, before, or after theremoval of the bonding apparatus 26 from the lead finger.

Referring to drawing FIG. 8, if desired to have additional clamping ofthe lead finger 14, either a conventional clamp 22 and/or a secondindependent actuated lead clamp 70, having a lead finger penetratingportion 78 thereon, may be used with the bonding apparatus 26. Thesecond independent actuated lead clamp 70 may be actuated and moved fromthe lead finger 14 with, before, or after the removal of the bondingapparatus 26 from the lead finger. It will be understood that thealternative embodiments of the present invention, shown in the otherdrawing figures corresponding to those described hereinabove, are wirebonded in a similar fashion.

FIG. 29 is a flow chart of a typical process sequence for plasticpackage molding of a semiconductor device wire bonded to a lead frame bythe use of a lead support portion 25 of movable and/or adjustable arm 24according to the present invention. It should be noted that the solderdip/plate operation has been shown as one step for brevity; normally,plating would occur prior to trim and form.

FIGS. 30 and 31 show pre-molding and post-molding positions ofencapsulant during a transfer molding operation using a typical moldapparatus comprising upper and lower mold halves 500 and 502, each moldhalf including a platen 514 or 516 with its associated chase 518 or 520.Heating elements 522 are employed in the platens to maintain an elevatedand relatively uniform temperature in the runners and mold cavitiesduring the molding operation. FIG. 32 shows a top view of one side ofthe transfer mold apparatus of FIGS. 30 and 31. In the transfer moldapparatus shown, the encapsulant flows into each mold cavity 544 throughthe short end thereof.

In operation, a heated pellet of resin mold compound 530 is disposedbeneath ram or plunger 532 in pot 534. The plunger descends, melting thepellet and forcing the melted encapsulant down through sprue 536 andinto primary runner 538, from which it travels to transversely-orientedsecondary runners 540 and across gates 542 into and through the moldcavities 544 through the short side thereof flowing across the dieassemblies 100, wherein die assemblies 100 comprising dice 102 withattached lead frames 104 are disposed (usually in strips so that a stripof six lead frames, for example, would be cut and placed in and acrossthe six cavities 544 shown in FIG. 32). Air in the runners 538 and 540and mold cavities 544 is vented to the atmosphere through vents 546 and548. At the end of the molding operation, the encapsulant is “packed” byapplication of a higher pressure to eliminate voids and reducenon-uniformities of the encapsulant in the mold cavities 544. Aftermolding, the encapsulated die assemblies are ejected from the cavities544 by ejector pins 550, after which they are post-cured at an elevatedtemperature to complete cross-linking of the resin, followed by otheroperations, as known in the art, and set forth in FIG. 29 by way ofexample. It will be appreciated that other transfer molding apparatusconfigurations, as well as variations in the details of the describedmethod, are known in the art. However, none of such are pertinent to theinvention, and so will not be discussed herein.

Encapsulant flow in the mold cavities 544 is demonstrably non-uniform.The presence of the die assembly 100 comprising a die 102 with leadframe 104 disposed across the mid-section of a cavity 544 splits theviscous encapsulant flow front 106 into upper 108 and lower 110components. Further, the presence of the (relatively) large die 102,with its relatively lower temperature in the middle of a cavity 544,permits the flow front 106 on each side of the die 102 to advance aheadof the front which passes over and under the die 102. FIGS. 33 and 34show two mold cavity encapsulant flow scenarios where, respectively, thelower flow front 110 and the upper flow front 108 lead the overallencapsulant flow front 106 in the cavity 544 containing the die assembly100. FIG. 35 depicts the advance of a flow front 106 from above, beforeand after a die 102 is encountered, the flow being depicted astime-separated instantaneous flow fronts 106 a, 106 b, 106 c, 106 d, 106e and 106 f.

It will be understood that the present invention may have changes,additions, deletions, modifications, and a different sequence ofoperation which fall within the scope of the invention. For instance,the lead support portion may be actuated in various directions withrespect to the semiconductor device during the wire bonding process. Thelead support portion may be segmented or in multiple pieces, etc.

1. An apparatus for supporting at least one lead finger of at least onelead frame for a wire bonding process connecting the at least one leadfinger to a semiconductor device comprising: at least one support forpositioning below the at least one lead finger for the wire bondingprocess, a surface of the at least one support for contacting a bearingsurface and for moving on a portion thereof, the at least one supportincluding a portion for positioning at a location between the at leastone lead finger and the semiconductor device, the portion of the atleast one support contacting a lower surface of the at least one leadfinger located above the semiconductor device without providing supporttherefor; and a heating apparatus for heating at least the semiconductordevice.
 2. The apparatus of claim 1, wherein the heating apparatusincludes a heating apparatus for heating the bearing surface.
 3. Theapparatus of claim 1, wherein the at least one support includes aportion for supporting more than the at least one lead finger.
 4. Theapparatus of claim 3, wherein the portion of the at least one supportcomprises a portion for positioning adjacent a semiconductor device. 5.The apparatus of claim 3, wherein the portion of the at least onesupport comprises a portion for positioning adjacent a semiconductordevice for exerting a force of a bonding apparatus to substantiallyapply the force against the portion.
 6. The apparatus of claim 3,wherein the portion of the at least one support comprises a portion forsubstantially preventing an application of force on a die by a bondingapparatus.
 7. The apparatus of claim 3, wherein the portion of the atleast one support comprises a portion for resisting a force ofsubstantially 50 to 100 grams.
 8. The apparatus of claim 3, wherein theportion of the at least one support comprises a portion for positioningbetween the at least one lead finger and the semiconductor device. 9.The apparatus of claim 1, wherein the at least one support includes aplurality of portions for supporting more than an individual lead fingerof the at least one lead frame.
 10. The apparatus of claim 1, furthercomprising an apparatus for moving the at least one support on thebearing surface.
 11. An apparatus used in a portion of wire bondingoperation for supporting at least one lead finger of at least one leadframe for a wire bonding process for connecting the at least one leadfinger to a semiconductor device comprising: at least one support forpositioning below the at least one lead finger for the wire bondingprocess, a surface of the at least one support for contacting a bearingsurface and for moving on a portion thereof, the at least one supportincluding a portion for positioning at a location between the at leastone lead finger and the semiconductor device, the portion of the atleast one support contacting a lower surface of the at least one leadfinger located above the semiconductor device without providing supporttherefor.